Title: Baclofen
CAS Registry Number: 1134-47-0
CAS Name: b-(Aminomethyl)-4-chlorobenzenepropanoic acid
Additional Names: b-(aminomethyl)-p-chlorohydrocinnamic acid; g-amino-b-(p-chlorophenyl)butyric acid; b-(4-chlorophenyl)GABA
Manufacturers' Codes: Ba-34647
Trademarks: Baclon (Leiras); Clofen (Alphapharm); Lioresal (Novartis)
Molecular Formula: C10H12ClNO2
Molecular Weight: 213.66
Percent Composition: C 56.21%, H 5.66%, Cl 16.59%, N 6.56%, O 14.98%
Literature References: Specific GABA-B receptor agonist. Prepn: NL 6407755; H. Keberle et al., US 3471548 (1965, 1969 both to Ciba). Toxicity study: T. Tadokoro et al., Osaka Daigaku Igaku Zasshi 28, 265 (1976), C.A. 88, 183016u (1978). Comprehensive description: S. Ahuja, Anal. Profiles Drug Subs. 14, 527-548 (1985). Review of pharmacology and therapeutic efficacy in spasticity: R. N. Brogden et al., Drugs 8, 1-14 (1974); of intrathecal use in spinal cord injury: K. S. Lewis, W. M. Mueller, Ann. Pharmacother. 27, 767-774 (1993). Clinical evaluation in reflex sympathetic dystrophy: B. J. van Hilten et al., N. Engl. J. Med. 343, 625 (2000).
Properties: Crystals from water, mp 206-208° (Keberle); 189-191°, (Uchimaru). LD50 in male mice, rats (mg/kg): 45, 78 i.v.; 103, 115 s.c.; 200, 145 orally (Tadokoro).
Melting point: mp 206-208° (Keberle); 189-191°, (Uchimaru)
Toxicity data: LD50 in male mice, rats (mg/kg): 45, 78 i.v.; 103, 115 s.c.; 200, 145 orally (Tadokoro)
Derivative Type: Hydrochloride
Molecular Formula: C10H13Cl2NO2
Molecular Weight: 250.12
Percent Composition: C 48.02%, H 5.24%, Cl 28.35%, N 5.60%, O 12.79%
Properties: mp 179-181°.
Melting point: mp 179-181°
Therap-Cat: Muscle relaxant (skeletal).
Keywords: Muscle Relaxant (Skeletal).
Bactericidal Permeability-Increasing Protein Bacteriorhodopsin Badische Acid Baicalein Bakankosin

Systematic (IUPAC) name
(RS)-4-amino-3-(4-chlorophenyl)butanoic acid
Clinical data
Trade names Lioresal, Liofen
AHFS/ monograph
Licence data US FDA:link
Pregnancy cat. C (US)
Legal status -only (US)
Routes Oral, intrathecal
Pharmacokinetic data
Bioavailability well absorbed
Protein binding 30%
Metabolism 85% excreted in urine/faeces unchanged. 15% metabolised by deamination
Half-life 1.5 to 4 hours
Excretion renal (70-80%)
CAS number 1134-47-0 YesY
ATC code M03BX01
PubChem CID 2284
IUPHAR ligand 1084
DrugBank DB00181
ChemSpider 2197 YesY
KEGG D00241 YesY
Chemical data
Formula C10H12ClNO2 
Mol. mass 213.661 g/mol
 YesY (what is this?)  (verify)

Baclofen (brand names Kemstro, Lioresal, Liofen, Gablofen, Beklo and Baclosan) is a derivative of gamma-aminobutyric acid (GABA). It is primarily used to treat spasticity and is in the early research stages for use for the treatment of alcoholism. It is also used by compounding pharmacies in topical pain creams as a muscle relaxant.

It is an agonist for the GABAB receptors.[1][2] Its beneficial effects in spasticity result from actions at spinal and supraspinal sites. Baclofen can also be used to treat hiccups, and has been shown to prevent rises in body temperature induced by the drug MDMA in rats.[3]

A beneficial property of baclofen is that tolerance does not seem to occur to a significant degree — baclofen retains its therapeutic anti-spasmodic effects even after many years of continued use.[4] Newer studies, however, indicate that tolerance may develop in some patients receiving intrathecal baclofen treatment.[5][6][7]

Oral dosage must be carefully regulated; significantly high doses of the drug, particularly 80 mg per day or higher, can cause excessive ataxia and/or drowsiness that can interfere with daily function.[citation needed]